Image Scanner and Image Scanning Method

ABSTRACT

An image scanner includes a transparent plate, a scanning device, a driving device, a positioning member, a light absorbing portion and a white reference portion. The transparent plate has an original placing surface. The scanning device irradiates an original with light by means of a light source and scans reflected light from the original. The driving device reciprocates the scanning device along the transparent plate. The positioning member positions the original placed on the original placing surface of the transparent plate. The light absorbing portion, which is disposed on the original placing surface side of the positioning member and at substantially a central portion of the positioning member in moving directions of the scanning device, absorbs ambient light entering to the original placing surface side of the positioning member through the transparent plate. The white reference portion is provided to the original placing surface side of the positioning member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.14/148,190, filed Jan. 6, 2014, which is a continuation of U.S.application Ser. No. 13/551,646, filed Jul. 18, 2012, now U.S. Pat. No.8,659,802 which is a continuation of U.S. application Ser. No.12/619,241, filed Nov. 16, 2009, now U.S. Pat. No. 8,253,986, which wasa divisional application of U.S. application Ser. No. 11/190,017, filedJul. 27, 2005, now U.S. Pat. No. 7,639,404, which claims the benefit ofJapanese Patent Application No. 2004-219050 filed Jul. 27, 2004 andJapanese Patent Application No. 2005-158815 filed May 31, 2005 in theJapanese Patent Office, the disclosures of which are incorporated hereinby reference.

BACKGROUND

The present invention relates to an image scanner, in which an originalplaced on an original placing surface of a transparent plate is scannedby a scanning device that is disposed opposite to the original placingsurface with respect to the transparent plate, irradiates the originalwith light by means of a light source and scans the reflected light fromthe original, and to an image scanning method.

In a known example of conventional image scanners, a platen made oftransparent glass is attached to an upper portion of a box housing withthe upper portion opened, and a scanning device, such as a Contact ImageSensor (hereinafter referred to as “CIS”), is reciprocably providedunder the platen. In the image scanner, an original is placed on theplaten with a surface to be scanned facing down, and an image on theoriginal is optically scanned by using the CIS. Then, a resulting lightsignal is converted into an electric signal to create image data.

In such an image scanner provided with a CIS, there are differences inoptical properties among light receiving elements, and unevenness inilluminance among individual light sources. This sometimes results invariation in scanned values that is undesirably large for creation ofimage information. It is, therefore, necessary to perform somecorrection of the differences in optical properties among lightreceiving elements and of the unevenness in illuminance among individuallight sources prior to image scanning by the CIS.

Generally, scanning of a white plate or a white roller is performed witha light source turned off prior to image scanning by the CIS, and theresulting light signal is converted into an electric signal. Theelectric signal is stored in a buffer memory as black image data. Then,the correction of image data of an original is performed based on theblack image data. This may compensate for differences in opticalproperties among light receiving elements.

Further correction is performed as disclosed in Publication ofUnexamined Japanese Patent Application No. 2000-115473. Specifically,the light source of the CIS is turned on, and the reflected lightobtained from the white plate or the white roller as a white referenceis focused onto light receiving elements and is scanned. The resultinglight signal is converted into an electric signal, and the electricsignal is stored in a buffer memory as white image data. Then, thecorrection of image data of the original is performed based on the whiteimage data. This may compensate for unevenness in illuminance amongindividual light sources.

The image scanner is provided with an original pressing plate forcovering the platen during scanning of the original. The originalpressing plate is arranged so as to be openable/closable in a verticaldirection (i.e., in upper and lower directions). However, image scanningof a thick original, such as a book original, using the CIS is performedwith the original pressing plate opened with respect to the platen,while the spine of the book original is pressed downward in order toprevent causing a shadow from the binding margin.

SUMMARY

Image scanning performed with the original pressing plate opened leadsto a problem that ambient light is allowed to enter the inside of theimage scanner through the platen. Ambient light here means indoor andoutdoor light entering the inside of the image scanner from transparentmembers, such as the platen, or openings of the image scanner. Morespecifically, ambient light entering the scanner through the platen maybe reflected and travel through the platen, and may reflect on, forexample, an internal surface of the housing after passing through theplaten. Such ambient light may enter the white plate or the white rolleras a white reference.

When the above described corrections are performed with the entry ofambient light, ambient light will cause the output of a black referenceto be larger than an output of a proper black reference. That is, blackimage data is obtained as an output larger than proper black image datacorrespondingly to the amount of ambient light. Ambient light will alsocause the output of a white reference to be larger than an output of aproper white reference. That is, white image data is obtained as anoutput larger than a proper white image data correspondingly to theamount of ambient light.

When corrections of image data obtained by image scanning of an originalare performed using image data of black and white influenced by ambientlight as described above, the white color in the original appearsdarker, and a darker image is provided. Specifically, since an outputcorresponding to the white of an original without an influence byambient light is smaller than white image data with an influence byambient light, the white is regarded as having a brightness lower than aproper white and corrected to a light gray level. As a result, a scannedimage in an area of the original where ambient light does not enterbecomes darker.

Especially, a black image having a lower black level is blurred.Specifically, an output curve of the CIS presents a gentle slopeindicating small output differences on a black level side. Accordingly,when an output of black image data becomes larger due to an influence byambient light, outputs corresponding to from a black level to a darkgray level of the original without an influence by ambient light becomessmaller than the black image data. As a result, outputs corresponding tofrom a black level to a dark gray level are all regarded as black in acorrected scanned image.

Such an influence by ambient light presents a problem particularlysignificant in an image scanner provided, in addition to the platen,with a slit glass for scanning an original conveyed by an originalconveying apparatus, since an upper area over the slit glass is exposedallowing ambient light to enter.

More specifically, when the platen has an FBS area as a flat bed scanner(hereinafter referred to as “FBS”) and an ADF area for scanning anoriginal conveyed by an original conveying apparatus, such as an autodocument feeder (hereinafter referred to as “ADF”), and a whitereference portion is provided to an original placing surface side of apositioning member that divides into these areas, the ADF area remainsexposed even if the FBS area is substantially covered with an original.Accordingly, ambient light enters the image scanner through the ADFarea, and then enters the original placing surface side of thepositioning member. On the contrary, most part of the original in theFBS area is not subject to an influence of ambient light since ambientlight is substantially blocked by the original. Thus, the abovedescribed problem is likely to be caused.

The present invention, relating to an image scanner, in which anoriginal placed on an original placing surface of a transparent plate isscanned by a scanning device that is disposed opposite to the originalplacing surface with respect to the transparent plate, irradiates theoriginal with light by means of a light source and scans the reflectedlight from the original, and to an image scanning method, has an objectto provide a device that prevents an influence of ambient light on awhite reference portion provided to an original placing surface side ofa positioning member, thereby to achieve an improved scanned imagequality.

In one aspect of the present invention, there is provided an imagescanner which comprises: a transparent plate, a scanning device, adriving device, a positioning member, a light absorbing portion, and awhite reference portion. The transparent plate has an original placingsurface for placing an original thereon. The scanning device, which isdisposed opposite to the original placing surface with respect to thetransparent plate, irradiates the original with light by means of alight source and scans the reflected light from the original. Thedriving device reciprocates the scanning device along the transparentplate. The positioning member positions the original placed on theoriginal placing surface of the transparent plate. The light absorbingportion is disposed on the original placing surface side of thepositioning member and at substantially a central portion of thepositioning member in moving directions of the scanning device. Thelight absorbing portion absorbs ambient light traveling in thetransparent plate. The white reference portion is provided to theoriginal placing surface side of the positioning member.

An original to be image scanned is placed on the original placingsurface of the transparent plate in accordance with the positioningmember. While the scanning device is moved by the driving device, thescanning device irradiates light to the original from the light source,and scans the reflected light. Thus, image scanning of the original isperformed.

Prior to the image scanning, the scanning device is moved by the drivingdevice to a position corresponding to the light absorbing portion and aposition corresponding to the white reference portion. Then, blackreference data is obtained with respect to the light absorbing portion,and white reference data is obtained with respect to the white referenceportion. When an area of the original placing surface, on which theoriginal is not placed, is exposed to the outside, ambient light entersinside the image scanner through the area. The ambient light, which hasentered the transparent plate from the outside, is reflected in thetransparent plate, and may enter the original placing surface side ofthe positioning member. Also, the ambient light may pass through thetransparent plate, be reflected by an internal surface of a main body(i.e., a housing) of the image scanner, again pass through thetransparent plate, and enter the original placing surface side of thepositioning member. On the original placing surface side of thepositioning member, the light absorbing portion absorbs the ambientlight which has entered thereinto.

Accordingly, an influence of ambient light on black reference data canbe prevented when black reference data is to be obtained with respect tothe light absorbing portion. It is, therefore, possible to obtainaccurate black reference data corresponding to the black color of theoriginal, and thereby to prevent deterioration of image quality of ascanned image in the case of image scanning with entry of ambient light.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be describedhereinafter with reference to the drawings, in which:

FIG. 1A is a perspective view showing a structure of an image scannerwith a main body cover in a closed state;

FIG. 1B is a perspective view showing a structure of the image scannerwith the main body cover in a opened state;

FIG. 2 is a plan view showing a structure of an upper portion of ascanner main body of the image scanner;

FIGS. 3A and 3B are diagrammatic cross-sectional views along alongitudinal direction of the image scanner;

FIG. 4 is a block diagram showing an electrical structure of the imagescanner;

FIG. 5A is a plan view showing an under surface of a positioning member;

FIG. 5B is a cross-sectional view taken along line 5B-5B in FIG. 5A;

FIG. 6 is a flowchart for illustrating an image scanning processperformed by the image scanner;

FIG. 7 is a flowchart for illustrating a first process of light amountadjustment and shading data calculation;

FIG. 8 is a flowchart for illustrating a second process of light amountadjustment and shading data calculation;

FIGS. 9A and 9B are explanatory views showing a structure around aplaten glass in Embodiment 1;

FIG. 10 is an explanatory view showing an operation of an image sensorduring the first process of light amount adjustment and shading datacalculation;

FIG. 11 is an explanatory view showing an operation of the image sensorduring the second process of light amount adjustment and shading datacalculation;

FIG. 12 is an explanatory view showing a structure around the platenglass in Embodiment 2; and

FIG. 13 is a flowchart for illustrating a third process of light amountadjustment and shading data calculation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

(a) Referring to FIGS. 1A, 1B, 2, 3A and 3B, an entire structure of animage scanner 1 of Embodiment 1 will be described below.

The image scanner 1 of Embodiment 1 is configured as a flatbed typescanner provided with a main body cover 5 upwardly openable with respectto a scanner main body 3. The scanner main body 3 has a box shape withan opening in an upper portion thereof. An image sensor (a CIS) 21 isarranged within the scanner main body 3, so as to be reciprocable in asub scanning direction (i.e., in the right and left directions in FIGS.3A and 3B). A platen glass (a transparent plate) 13 is fixed withtwo-sided tape to an upper frame 20 of the scanner main body 3 having anopening so as to cover the opening. The platen glass 13, which is madeof transparent glass or resin, has an upper surface constituting anoriginal placing surface on which an original is placed.

The image scanner 1 may be embodied as part of a multifunction apparatusintegrally provided with a scanner function, a printer function and afacsimile function. It is to be understood, however, that functionsother than a scanner function are optional in the present invention, andthat the present invention may be embodied as an exclusive scanner.

The upper surface of the platen glass 13 can be covered with the mainbody cover 5 that is openable/closable in upper and lower directionswith respect to a rear side of the scanner (an upper side in FIG. 2) asa rotation center. An original conveying device 40, provided on one endportion of the main body cover 5, can cover the platen glass 13 alongwith the main body cover 5. A pressing member, including sponge and awhite plate, is disposed on an under surface of the main body cover 5 ata position corresponding to the platen glass 13. An original placed onthe platen glass 13 is pressed by the pressing member. In FIG. 1A, themain body cover 5 is closed to cover the platen glass 13. In FIG. 1B,the main body cover 5 is opened to expose an entire area of the platenglass 13.

The scanner main body 3 is provided with an operating portion 15including a variety of switches, such as a numeric keypad and others,and an LCD panel in a front portion (a lower side in FIG. 2) thereof.When a command is inputted by operating a key in the operating portion15, the command is executed by an after-mentioned CPU 101. The imagescanner 1 may be configured such that the image scanner 1 is connectedto an external information device, such as a computer, and commandstransmitted from software installed in the computer, such as a scannerdriver, are executed by the CPU 101.

The upper frame 20 of the scanner main body 3 has an opening, and theplaten glass 13 is fixed to the upper frame 20 so as to cover theopening.

An image sensor 21 is arranged within the scanner main body 3, so as tobe reciprocable in the sub scanning direction (i.e., in the right andleft directions in FIGS. 3A and 3B). The image sensor 21 is positionedunder the platen glass 13, while the original placing surface is theupper surface of the platen glass 13. In other words, the image sensor21 is positioned opposite to the original placing surface with respectto the platen glass 13.

The image sensor 21 is a contact-type image sensor including point lightsources (hereinafter referred to as the “light sources”), a SELFOC®lens, and a multiplicity of light receiving elements. The light sourcesare, for example, three colors of LEDs (R, G, and B), which irradiatelight onto an original P on the platen glass 13. The SELFOC® lens is forfocusing the reflected light onto the light receiving elements. Thelight receiving elements are arranged in a row at predetermined spacingsso as to face upward. The length of the arranged light receivingelements in the image sensor 21 is approximately the same as a length ofthe platen glass 13.

In the scanner main body 3, a driving device is provided. The drivingdevice includes a DC motor 23 arranged with its motor shaft orienteddownward at one end of the scanner main body 3 in a longitudinaldirection (i.e., in the sub scanning direction), a pulley 25 a attachedto the motor shaft, and a pulley 25 a disposed at the other end of thescanner main body 3. The driving device further includes an endless belt25 b tensioned between these pulleys 25 a. The driving device enablesthe image sensor 21 to move in a sub scanning direction (in thelongitudinal direction of the scanner main body).

Accordingly, as described below, the image sensor 21 is configured to bereciprocable between a stationary original scanning area (a firstscanning area) 11 and a moving original scanning area (a second scanningarea) 12 of the platen glass 13.

On the original placing surface side of the platen glass 13, apositioning member 17 is provided. The positioning member 17 divides theoriginal placing surface of the platen glass 13 into a plurality ofareas, i.e., the stationary original scanning area 11 and the movingoriginal scanning area 12. The stationary original scanning area 11 is asurface on which an original P is placed when the image scanner is usedas an FBS. The moving original scanning area 12 is a surface to scan anoriginal P conveyed by using the original conveying device 40. As shownin FIG. 2, the platen glass 13 is divided into two areas by thepositioning member 17, such that a narrow specific area is formed on aleft side in the sub scanning direction of the image scanner 1 (i.e., inthe right and left directions in FIG. 2) and a wide specific area isformed on a right side in the sub scanning direction on which anoriginal P of a maximum scannable size can be placed. The narrowspecific area on the left side is the stationary original scanning area11, and the wide specific area on the right side is the moving originalscanning area 12.

When the image scanner is used as an FBS, an original to be scanned P isplaced facing down on the platen glass 13 in a state as shown in FIG.1B. Specifically, the original P is placed with the surface to bescanned facing down on the stationary original scanning area 11 of theplaten glass 13 using the positioning member 17 as an edge reference forthe original P. The main body cover 5 is rotated downward around therotation center so as to press the original P, as shown in FIG. 1A, andthen image scanning of the original P is preformed. Specifically, asshown in FIG. 3B, the image sensor 21 fixed to the endless belt 25 birradiates light using the light sources while moving in a rightdirection of FIG. 3B due to the rotation of the DC motor 23. Reflectedlight from the original P is focused through the lens onto the lightreceiving elements, and light signals are converted into electricalsignals.

As shown in FIGS. 3A and 3B, the original conveying device 40 (ADF) ismounted on the main body cover 5. The original conveying device 40includes a paper feed tray 41, a paper exit tray 42, and a conveyingpath 55. The paper feed tray 41 is for loading the originals P with eachsurface to be scanned facing down. The paper exit tray 42 is providedabove the paper feed tray 41 for stacking the originals P with eachscanned surface facing up once scanning is completed. The conveying pathis formed between the paper feed tray 41 and the paper exit tray 42 soas to define a reverse U-shaped turn. The paper feed tray 41 and thepaper exit tray 42 are arranged to be shifted with each other in ahorizontal direction so as to provide an open space over the paper feedtray 41. This leads to an advantage that the setting of the originals Pon the paper feed tray 41 is easier as compared with a case of disposingthe paper exit tray 42 right above the paper feed tray 41. By providingthe paper feed tray 41 and the paper exit tray 42, originals P beforeand after the scanning can be held separately on the paper feed tray 41and the paper exit tray 42.

The originals P, loaded on the paper feed tray 41, are drawn out bypaper feed rollers 44 and 45, disposed substantially under the paperfeed tray 41, and are conveyed downstream sheet by sheet. A set ofrollers consisting of conveyer rollers 47 and 48 are disposed downstreamfrom the paper feed rollers 44 and 45 for conveying the originals Ptoward the moving original scanning area 12 at the lowermost position.An upper plate 49 is disposed so as to face the moving original scanningarea 12 of the platen glass 13 at a predetermined distance apart fromthe platen glass 13. The conveyed originals P are scanned sequentiallyby the image sensor 21 waiting under the moving original scanning area12 (i.e., waiting at an ADF scanning position).

An ascending member 20 a is provided near one end (a left end in FIG. 3)of the platen glass 13 so as to deflect the front end of each of theoriginals P that have moved on the platen glass 13. Each of theoriginals P is conveyed with a change in direction upward by a set ofconveyer rollers 51 and 52, and is discharged by discharge rollers 53and 54 on the paper exit tray 42 with a scanned surface facing up.

The configuration of the conveying device 40 is described as above onlyby way of example. It is to be understood that the configuration of theconveying device 40 may be modified into the configurations of otherknown conveying devices. For example, the relative positions of thepaper feed tray 41 and the paper exit tray 42 may be changed. Theconfigurations and arrangement of rollers, such as the paper feedrollers 44 and 45, the conveyer rollers 47 and 48, and the dischargerollers 53 and 54, as well as the conveying path 55 may also be changed.

(b) The structure of the positioning member 17 will now be describedwith reference to FIGS. 5A and 5B. In FIG. 5A, showing an under surface(a glass abutting surface) of the positioning member 17, upper and lowerdirections indicate a main scanning direction and correspond to theupper and lower directions in FIG. 2. A left direction in FIG. 5Acorresponds to the left direction in FIG. 2. Accordingly, a left side ofthe positioning member 17 corresponds to the moving original scanningarea 12, while a right side of the positioning member 17 corresponds tothe stationary original scanning area 11 in FIG. 5A.

The positioning member 17 is a substantially rectangular plate memberhaving a length in the main scanning direction (i.e., in the upper andlower directions in FIG. 5A) the same as the length of the platen glass13 in the main scanning direction. Accordingly, when the positioningmember 17 is arranged on the platen glass 13 along the main scanningdirection, as shown in FIG. 2, the positioning member 17 has enoughlength to extend from one end to the other end of the platen glass 13.

Substantially the entire under surface of the positioning member 17 iscovered with a white reference portion 17 a made of a white thin platemember. A black reference portion 17 b, made of a black thin platemember, is attached onto the under surface of the white referenceportion 17 a. The black reference portion 17 b is arranged such thatapproximately one third of the white reference portion 17 a from a leftend thereof is exposed without being covered with the black referenceportion 17 b. In other words, an area of approximately two thirds of thewhite reference portion 17 a, starting from a position of approximatelyone third of the white reference portion 17 a on the side of the movingoriginal scanning area 12 toward the right direction (toward thestationary original scanning area 11), is covered with the blackreference portion 17 b.

The above area of the white reference portion 17 a exposed without beingcovered with the black reference portion 17 b is used for obtaining theafter-mentioned white reference data and for light amount adjustment. Acenter part of an area of the black reference portion 17 b,corresponding to approximately one third of the white reference portion17 a on the right side, is cut out, and thereby the white referenceportion 17 a is exposed therein. A line defined by a left end 17 f ofthe black reference portion 17 b, that is, a boundary between the whitereference portion 17 a and the black reference portion 17 b, is areference position for the sub scanning of the image sensor 21.Specifically, a home position HP (a waiting position) is determinedbased on the left end 17 f at the time of initialization when the poweris turned on and after completion of scanning.

By cutting out the center part of the black reference portion 17 b onthe right side, two boundaries between the white reference portion 17 aand the black reference portion 17 b in the main scanning direction areprovided. These two boundaries are used as reference positions 17 d inthe main scanning of the image sensor 21. In the image scanner 1 ofEmbodiment 1, the center between the two reference positions 17 d isdefined as a center of each of the originals P.

At each of the above reference positions 17 d and 17 f, there is a clearchange in color (brightness) between the white color of the whitereference portion 17 a and the black color of the black referenceportion 17 b. Accordingly, the reference positions 17 d and 17 f can bedefinitely determined based on outputs of the image sensor 21.

An area of the black reference portion 17 b extending in the mainscanning direction of the image sensor 21, that is, an area around acenter of the positioning member 17 in the sub scanning direction of theimage sensor 21, is used for obtaining the after-mentioned blackreference data. The obtainment of the black reference data is performednot over an entire width of the black reference portion 17 b in the subscanning direction, but at a position 17 h corresponding to a mainscanning line along which the light receiving elements are aligned. Awidth of the black reference portion 17 b around the center thereof issufficiently wide for the position 17 h. The black reference portion 17b at least extends out to the left side, toward the moving originalscanning area 12 from the position 17 h. The black reference portion 17b may, of course, extend out to the right side, toward the stationaryoriginal scanning area 11 from the position 17 h.

A clear two-sided tape 17 c is applied to a right end area of the undersurface of the positioning member 17. The two-sided tape 17 c consistsof a thick two-sided tape 17 c 1 applied to a center portion in theupper and lower directions in FIG. 5A and thin two-sided tapes 17 c 2applied to an upper end portion and an lower end portion in FIG. 5A. Athickness difference between the two-sided tape 17 c 1 and the two-sidedtape 17 c 2 corresponds to a thickness difference between the whitereference portion 17 a and the black reference portion 17 b. The whitereference portion 17 a is cut off in accordance with the shape of thetwo-sided tape 17 c 1 in an area at which the two-sided tape 17 c 1 isapplied. That is, the two-sided tape 17 c 1 is applied directly to thepositioning member 17. On the contrary, the two-sided tapes 17 c 2 areapplied to the white reference portion 17 a and the black referenceportion 17 b.

As shown in FIG. 5B, a left end of the white reference portion 17 aincludes an extending portion which extends further from the positioningmember 17 in a left direction. A clear tape 17 e is applied to an uppersurface of the extending portion. The clear tape 17 e has a right endfixed to the positioning member 17 and a left end extending further fromthe white reference portion 17 a in the left direction.

As described above, the white reference portion 17 a and the blackreference portion 17 b are arranged on the under surface of thepositioning member 17, and the positioning member 17 is fixed to theupper surface of the platen glass 13 in close contact with each otherwith the two-sided tapes 17 c 1, 17 c 2 and the two-side tape 17 e. Thatis, the white reference portion 17 a and the black reference portion 17b are arranged on the original placing surface side of the positioningmember 17. Accordingly, the white reference portion 17 a is arranged onthe original placing surface side of the positioning member 17 and onthe side of the moving original scanning area 12. The black referenceportion 17 b is arranged on the original placing surface side of thepositioning member 17 and around the center of the positioning member 17in the sub scanning direction of the image sensor 21.

(c) An electrical structure of the image scanner 1 will be describedhereinafter with reference to FIG. 4. A CPU 101 performs control ofvarious components in the image scanner 1, such as control offorward/reverse rotation of the motor 23, control of speed, and controlof the turning on/off of the light sources provided in the image sensor21, based on control programs stored in a ROM 102. The ROM 102 storesprograms for controlling the image scanner 1.

A RAM 103 is a memory for temporarily storing image data scanned by theimage sensor 21 and image data from a PC connected to the image scanner1. The RAM 103 includes at least a black reference buffer area 103 athat stores black reference data for correcting gradient propertiesamong the light receiving elements, and a white reference buffer area103 b that stores white reference data for correcting variation in lightamount among the light sources.

A correction circuit 104 performs processes, such as black correction,white correction, and gamma correction, line by line with respect tocolors R, G, and B. Specifically, various corrections such as shadingcorrection are performed on image data of an original P scanned by theimage sensor 21.

An image processing portion 106 performs processes, such as smoothingand emphasizing of corrected image data, converting RGB data intoprintable Cyan-Magenta-Yellow-Black (CMYK) data, and others.

(d) Processes performed by the CPU 101 of the image scanner 1 will nowbe described with reference to FIGS. 6-10.

First, processes performed by the CPU 101 will be describedschematically using the flowchart in FIG. 6. In Step 100, the CPUperforms light amount adjustment and shading data calculation. Thisprocess will be described in detail later.

In Step 110, the CPU 101 performs scanning of an original P andgenerates an image signal.

Scanning of the original P placed on the stationary original scanningarea 11 of the platen glass 13 is performed as described below. The CPU101 controls the motor 23 and simultaneously makes the image sensor 21scan the original P placed on the stationary original scanning area 11.That is, the CPU 101 makes the image sensor 21 scan the original P,while moving the image sensor 21.

Scanning of an original P conveyed by the original conveying device 40is performed as described below. The CPU 101 fixes the image sensor 21under the moving original scanning area 12. Then, the CPU 101 controlsthe original conveying device 40 to convey an original P, placed on thepaper feed trays 41, toward the original scanning area 12. While theoriginal P passes through the original scanning area 12, the CPU 101makes the image sensor 21 scan the original P.

An image signal output by the image sensor 21, which has scanned theoriginal P, is digitized by an internal circuit. Well-known shadingcorrection or the like is performed on the digitized image signal by thecorrection circuit 104, based on shading data created and updated asdescribed later. The image signal after the shading correction is storedonce in the RAM 103, and then is provided to an external personalcomputer or an image forming device through an interface 105 by anoperation of the CPU 101.

Second, a process of light amount adjustment and shading datacalculation performed by the CPU 101 will be described using FIGS. 7, 9and 10.

(Light Amount Adjustment and Shading Data Calculation Process 1)

Before this process is started, the image sensor 21 is located at a homeposition HP. The home position HP is a waiting position which is closerto the white reference portion 17 a than to the black reference portion17 b (see FIG. 10). The waiting position is determined based on thereference position 17 f in the sub scanning direction shown in FIG. 5A.

Specifically, when the power is turned on, the CPU 101 makes the imagesensor 21 scan the reference position 17 f while moving under thepositioning member 17 with the light sources on. Since the referenceposition 17 f is a boundary between the white color and the black color,outputs of the light receiving elements change due to changes in thereflected lights from these colors. The CPU 101 determines the referenceposition 17 f based on output changes of the image sensor 21. Then theimage sensor 21 is moved to a waiting position which is determined as aposition at a specified distance apart from the reference position 17 ftoward the exposed area of the white reference portion 17 a, i.e.,toward the moving original scanning area 12 (a waiting step). Thewaiting position is preferably located in the vicinity of thepositioning member 17 with the object of speeding up the light amountadjustment and the obtainment of corrected data.

In Step 200 in FIG. 7, when the start button in the operating portion 15is pressed down, the motor 23 is rotated by a command issued by the CPU101. Then, the image sensor 21 starts to move away from the homeposition HP, in order to obtain black reference data and white referencedata. After a movement of a specific distance from the home position HP,the image sensor 21 stops under the black reference portion 17 b (themovement from (1) HP to (2) black reference portion in FIG. 10). Afterthe movement, the image sensor 21 is positioned right under the blackreference portion 17 b, as shown in FIG. 9B.

In Step 210 (a black reference data obtaining step), black referencedata is obtained. Specifically, scanning of the black reference portion17 b is performed a plurality of times with the light sources of theimage sensor 21 turned off. Then, the obtained data is divided by thenumber of times the scanning was performed with respect to each of thelight receiving elements in order to calculate an average, and theaverage data is stored in the black reference buffer area 103 a of theRAM 103 as the black reference data.

In Step 220, upon storing the black reference data, the motor 23 isdriven again to move the image sensor 21 by a predetermined distance toa position under the white reference portion 17 a (the movement from (2)BLACK REFERENCE PORTION to (3) WHITE REFERENCE PORTION in FIG. 10).

In Step 230, light adjustment for the white reference portion 17 a isperformed. Specifically, first, light with a sufficiently small lightamount is irradiated to the white reference portion 17 a from the lightsources of the image sensor 21, and the reflected light is scanned bythe light receiving elements. When the light amount of the light sourcesis small, the output of the light receiving elements is accordinglysmall. The light amount is increased in a stepwise or continuous manneruntil the output of the light receiving elements reaches a desiredvalue. The light amount when the output of the light receiving elementsreaches the desired value is store in the RAM 103 as an adjusted lightamount value. The desired value of the output of the light receivingelements is determined such that the output of white reference dataagainst black reference data gives a desired value.

In Step 240 (a white reference data obtaining step), the image sensor 21scans the white reference portion 17 a. Specifically, light with theadjusted light amount value is irradiated to the white reference portion17 a from the light sources of the image sensor 21, and the reflectedlight from the white reference portion 17 a is scanned by the lightreceiving elements. Thus, white reference data is obtained.

In this process, the CPU 101 rotates the motor 23 in forward and reversedirections, thereby to reciprocate the image sensor 21 under the whitereference portion 17 a. The range of reciprocation is between a point Acorresponding to a position 1 mm from a left end of the white referenceportion 17 a and a point B corresponding to a position 1 mm from a rightend of the white reference portion 17 a (see (3) WHITE REFERENCE PORTIONin FIG. 10). During the reciprocation, the light receiving elementsobtain a plurality of pieces of data at different positions in the whitereference portion 17 a. The obtained plurality of pieces of data aredivided by the number of times of scanning with respect to each of thelight receiving elements, and are stored in the white reference bufferarea 103 b of the RAM 103 as white reference data.

In Step 250, the CPU 101 creates black shading data by using the blackreference data obtained in Step 210, while creating white shading databy using the white reference data obtained in Step 240. The createdshading data of each color is stored in the RAM 103.

The created shading data of each color is also used for shadingcorrection of the image signal. The created shading data of each coloris updated each time it is newly created.

In Step 260, the CPU 101 moves the image sensor 21 to a scanning startposition. In the case of scanning an original conveyed by the originalconveying device 40, the scanning start position is the ADF scanningposition shown in FIG. 3A. In the case of scanning an original placed onthe stationary original scanning area 11, the scanning start position isunder the left end of the stationary original scanning area 11, as shownin FIG. 3B and indicated by (4) SCANNING START POSITION) in FIG. 10.Subsequently, as described above, image scanning of an original P isperformed by irradiating light to the original P from the light sourcesof the image sensor 21 and by scanning the reflected light by the lightreceiving elements.

(e) Advantages provided by the image scanner 1 of Embodiment 1 and animage scanning method using the image scanner 1 will be described below.

i) According to the image scanner 1 of Embodiment 1, the black referencedata is obtained while the image sensor 21 is under the black referenceportion 17 b. Since the black reference portion 17 b on the side of theoriginal placing surface (i.e., on the under surface) of the positioningmember 17. Accordingly, if an instruction to perform image scanning isprovided while the main body cover 5 is opened, that is, while thestationary original scanning area 11 and the moving original scanningarea 12 are exposed, ambient light is likely to enter. Particularly whena thick original P is to be scanned using the image scanner 1 as an FBS,it is difficult to completely close the main body cover 5. Also, sincethe original P is not placed on the moving original scanning area 12,ambient light is further likely to enter.

Such ambient light that has entered the side of the original placingsurface of the positioning member 17 is absorbed by the black referenceportion 17 b. Accordingly, ambient light that has entered the blackreference portion 17 b will not be reflected to the image sensor 21.Then, obtainment of black reference data is performed with respect tothe black reference portion 17 b with the light sources of the imagesensor 21 turned off, and accurate black reference data can be obtainedwithout an influence of ambient light. It is, therefore, possible toobtain black reference data with a clear gradation and to performaccurate shading correction in the image scanner 1 of Embodiment 1.

ii) In Embodiment 1, the white reference portion 17 a and the blackreference portion 17 b are arranged on the side of the original placingsurface of (on the under surface of) the positioning member 17, and thepositioning member 17 is arranged on the upper surface of the originalplacing surface of the platen glass 13. Accordingly, the white referenceportion 17 a and the black reference portion 17 b are arranged on theupper surface of the original placing surface of the platen glass 13.

As a result, either of the distance between the image sensor 21 and thewhite reference portion 17 a, and the distance between the image sensor21 and the black reference portion 17 b, is the same as the distancebetween the image sensor 21 and an original P placed on the platen glass13. In other words, white reference data obtained with respect to thewhite reference portion 17 a and black reference data obtained withrespect to the black reference portion 17 b is based on the sameconditions as in the obtainment of image data of the original P. It is,therefore, possible to obtain accurate white reference data by using thewhite reference portion 17 a and accurate black reference data by usingthe black reference portion 17 b in the image scanner 1 of Embodiment 1.

iii) In Embodiment 1, as shown in FIGS. 5A and 5B, the white referenceportion 17 a and the black reference portion 17 b are adjacent to eachother. Accordingly, the moving distance of the image sensor 21 can bereduced when the image sensor 21 is moved from under the white referenceportion 17 a to under the black reference portion 17 b, or vice versa.This leads to a shortened time interval between the obtainment of whitereference data and the obtainment of black reference data. It is,therefore, possible to create the shading data in a short time.

iv) In Embodiment 1, as shown in FIGS. 5A and 5B, the black referenceportion 17 a is arranged so as to extend from the center of thepositioning member 17 in the sub scanning direction of the image sensor21 toward the moving original scanning area 12. Accordingly, the blackreference portion 17 b may have a sufficient area from the position 17h, at which black reference data is obtained, toward the moving originalscanning area 12 through which ambient light is likely to enter. It is,therefore, possible to further surely absorb, by means of the blackreference portion 17 b, ambient light which enters from the movingoriginal scanning area 12, is reflected in the platen glass 13, orpasses through the platen glass 13 and is reflected in the housing, andenters the side of the original placing surface of the positioningmember 17.

v) In Embodiment 1, the length of the black reference portion 17 b inthe main scanning direction is larger than the length of the platenglass 13 in the main scanning direction. That is, the black referenceportion 17 b extends from one end to the other end of the platen glass13. Accordingly, the black reference portion 17 b can sufficientlyabsorb ambient light traveling through the platen glass 13.

vi) In Embodiment 1, white reference data is obtained at a plurality ofpositions in the white reference portion 17 a while the image sensor 21is reciprocated. Accordingly, even if dust is attached to a part of thewhite reference portion 17 a, the influence of the dust can be reduced.Thus, accurate white reference data can be obtained.

vii) In Embodiment 1, the image sensor 21 obtains a plurality of piecesof black reference data. Accordingly, accurate black reference data canbe obtained without being influenced by variations in black referencedata.

viii) In Embodiment 1, when (Light Amount Adjustment and Shading DataCalculation Process 1) (see FIG. 7) is selected, black reference data isobtained first, and then white reference data is obtained. Thisfacilitates the easy creation of shading data.

(Process of Light Amount Adjustment and Shading Data Calculation 2)

In Embodiment 1, an alternative process of light amount adjustment andshading data calculation may be performed. The alternative process willbe described below with reference to FIGS. 8, 9 and 11.

Before the process is started, the image sensor 21 is located at thehome position HP. The method of making the image sensor 21 wait at awaiting position (a waiting step) is the same as described above.

In Step 300 in FIG. 8, when the start button in the operating portion 15is pressed down, the motor 23 is rotated by a command issued by the CPU101. Then, the image sensor 21 starts to move away from the homeposition HP in order to obtain black reference data and white referencedata. After a movement of a specific distance from the home position HP,the image sensor 21 stops under the white reference portion 17 a (themovement from (1) HP to (2) WHITE reference portion in FIG. 11). Afterthe movement, the image sensor 21 is positioned under the whitereference portion 17 a as shown in FIG. 9A.

In Step 310, the CPU 101 adjusts the light amount of the light sourcesof the image sensor 21 to be suitable for subsequent capturing of whitereference data. Although this light amount adjustment is the same as thelight amount adjustment shown in Step 230, black reference data has notyet been obtained. Prior to obtainment of black reference data, however,black reference data previously obtained at the previous image scanningis stored in the black reference buffer area 103 a of the RAM 103.Therefore, light amount adjustment is performed based on the previouslyobtained black reference data such that white reference data has adesired output.

In Step 320 (a white reference data obtaining step), the image sensor 21scans the white reference portion 17 a. In this case, the motor 23 isrotated in forward and reverse directions, thereby to reciprocate theimage sensor 21 under the white reference portion 17 a. The range ofreciprocation is between a point A corresponding to a position 1 mm froma left end of the white reference portion 17 a and a point Bcorresponding to a position 1 mm from a right end of the white referenceportion 17 a (see (2) WHITE REFERENCE PORTION in FIG. 11). During thereciprocation, the light receiving elements of the image sensor 21obtain a plurality of pieces of data at different positions in the whitereference portion 17 a. The obtained plurality of pieces of data aredivided by the number of times of scanning with respect to each of thelight receiving elements, and are stored in the white reference bufferarea 103 b of the RAM 103 as white reference data.

In Step 330, the CPU 101 moves the image sensor 21 from a position underthe white reference portion 17 a to a position under the black referenceportion 17 b (the movement from (2) WHITE REFERENCE PORTION to (3) BLACKREFERENCE PORTION in FIG. 11). After the movement, the image sensor 21is positioned right under the black reference portion 17 b, as shown inFIG. 9B. The CPU 101 turns off the light sources of the image sensor 21by the time the image sensor has reached a position under the blackreference portion 17 b.

In Step 340 (a black reference obtaining step), scanning is performed aplurality of times with the light sources of the image sensor 21 turnedoff in order to scan black reference data. Then, the obtained data isdivided by the number of times the scanning was performed with respectto each of the light receiving elements in order to calculate anaverage, and the average data is stored in the black reference bufferarea 103 a of the RAM 103 as black reference data.

In Step 350, the CPU 101 creates black shading data by using the blackreference data obtained in Step 340, while creating white shading databy using the white reference data obtained in Step 320. The createdshading data of each color is stored in the RAM 103.

In Step 360, the CPU 101 moves the image sensor 21 to a scanning startposition. In the case of scanning an original conveyed by the originalconveying device 40, the scanning start position is the ADF scanningposition shown in FIG. 3A. In the case of scanning an original placed onthe stationary original scanning area 11, the scanning start position isunder a left end of the stationary original scanning area 11 as shown inFIG. 3B and indicated by (4) SCANNING START POSITION in FIG. 11.Subsequently, as described above, image scanning of an original P isperformed by irradiating light to the original P from the light sourcesof the image sensor 21 and by scanning the reflected light by the lightreceiving elements.

When (Light Amount Adjustment and Shading Data Calculation Process 2)(see FIG. 8) is selected in Embodiment 1, the image sensor 21 moves inone direction from the home position through the position under thewhite reference portion 17 a to the position under the black referenceportion 17 b. This leads to a shortened moving distance of the imagesensor 21, and thereby to a reduced time required for the creation ofshading data.

Embodiment 2

The structure and operation of an image scanner 1 in Embodiment 2 arebasically the same as in Embodiment 1.

In Embodiment 2, however, a light absorbing portion 17 g is provided tothe positioning member 17 on a side of the moving original scanning area12, as shown in FIG. 12. The light absorbing portion 17 g is aplate-like member having a horizontal under surface and a sloping uppersurface lowered toward the outside. The under surface of the lightabsorbing portion 17 g is level with the white reference portion 17 a,the black reference portion 17 b and a mark portion 17 c, and is blackin color as with the black reference portion 17 b.

According to the image scanner 1 of Embodiment 2, ambient light enteringfrom the side of the moving original scanning area 12 can be absorbed bythe light absorbing portion 17 g. Therefore, ambient light entering intothe white reference portion 17 a can be further reduced, and therebyfurther accurate shading data can be created.

In Embodiment 2, an internal surface 3 a of a housing 3 is black andserves as an additional light absorbing portion. Accordingly, ambientlight, which has been transmitted through the platen glass 13 and hasreached the internal surface 3 a of the housing 3, is absorbed by theinternal surface 3 a before reaching the white reference portion 17 a.Therefore, ambient light entering into the white reference portion 17 acan be further reduced, and thereby further accurate shading data can becreated.

Embodiment 3

The structure and operation of an image scanner 1 in Embodiment 3 arebasically the same as in Embodiment 1.

In Embodiment 3, however, a process of light amount adjustment andshading data calculation is performed as shown in FIG. 13.

In Step 400, when the start button in the operating portion 15 ispressed down, the motor 23 is rotated by a command issued by the CPU101. Then, the image sensor 21 starts to move away from the homeposition HP in order to obtain black reference data and white referencedata. After a movement of a specific distance from the home position HP,the image sensor 21 stops under the white reference portion 17 a. Afterthe movement, the image sensor 21 is positioned under the whitereference portion 17 a, as shown in FIG. 9A. The HP as the waitingposition of the image scanner 21 and the method of making the imagesensor 21 wait at a waiting position (a waiting step) is the same as inEmbodiment 1.

In Step 410 (a black reference data obtaining process), scanning of thewhite reference portion 17 a is performed a plurality of times with thelight sources of the image sensor 21 turned off in order to scan blackreference data. Then, the obtained data is divided by the number oftimes the scanning was performed with respect to each of the lightreceiving elements in order to calculate an average, and the averagedata is stored in the black reference buffer area 103 a of the RAM 103as the black reference data.

In Step 420, the CPU 101 adjusts the light amount of the light sourcesof the image sensor 21 to be suitable for subsequent capturing of whitereference data. The method of light adjustment is the same as inEmbodiment 1.

In Step 430 (a white reference data obtaining step), the image sensor 21scans the white reference portion 17 a. In this case, the motor 23 isrotated in forward and reverse directions, thereby to reciprocate theimage sensor 21 under the white reference portion 17 a. The range ofreciprocation is between a point A corresponding to a position 1 mm froma left end of the white reference portion 17 a and a point Bcorresponding to a position 1 mm from a right end of the white referenceportion 17 a. During the reciprocation, the light receiving elementsobtain a plurality of pieces of data at different positions in the whitereference portion 17 a. The obtained plurality of pieces of data aredivided by the number of times of scanning with respect to each of thelight receiving elements, and are stored in the white reference bufferarea 103 b of the RAM 103 as white reference data.

In Step 440, the CPU 101 creates shading data by using the blackreference data obtained in Step 410 and the white reference dataobtained in Step 430. The created shading data is stored in the RAM 103.

In Step 450, the CPU 101 moves the image sensor 21 to a scanning startposition. Subsequently, in the same manner as in Embodiment 1, imagescanning of an original P is performed by irradiating light to theoriginal P from the light sources of the image sensor 21 and by scanningthe reflected light by the light receiving elements

In Embodiment 3, as described above, the black reference data isobtained by scanning the white reference portion 17 a with the lightsources of the image sensor 21 turned off.

According to Embodiment 3, obtainment of the black reference data andthe white reference data is performed with the image sensor 21positioned under the white reference portion 17 a. Therefore, the numberof movements of the image sensor 21 as well as the moving distance ofthe image sensor 21 can be reduced. This allows easy control of theimage sensor 21 and a reduction of time required for creating shadingdata.

It is to be understood that the present invention should not be limitedto the above described embodiments, but may be embodied in various formswithout departing from the spirit and scope of the present invention.

For example, the white reference portion 17 a and the black referenceportion 17 b may be reversely arranged in Embodiments 1 through 3. Thatis, an arrangement may be employed in which the black reference portion17 b is located on a side of the moving original scanning area 12 of theunder surface of the positioning member 17, and the white referenceportion 17 a is located in a center portion of the under surface of thepositioning member 17.

While the white reference portion 17 a and the black reference portion17 b are provided as separate members such that black reference portion17 b covers the white reference portion 17 a in Embodiments 1 through 3,the white reference portion 17 a and the black reference portion 17 bmay be provided as a single member by, for example, applying white colorand black color thereon.

Also, while a CIS is employed as an image sensor 21 serving as ascanning device in Embodiments 1 through 3, a charge-coupled device(CCD) image sensor in the reduction optical system, for example, may beemployed other than a contact-type image sensor, such as a CIS, as thescanning device in the present invention.

We claim:
 1. An image scanner, comprising: a single transparent plate; adividing member disposed on the single transparent plate and dividingthe single transparent plate into a first area and a second area byextending in a first direction, the dividing member including a whiteportion in contact with an upper surface of the single transparentplate; a scanning device configured to scan a first original placed onthe first area while moving along the first area, and to scan a secondoriginal being conveyed at the second area in a conveying directionwhile stopping at a position directly below the second area, theconveying direction being perpendicular to the first direction; aconveying device configured to convey the second original being scannedin the conveying direction at the second area; and a guide memberdisposed downstream of the second area in the conveying direction inwhich the second original being scanned is conveyed at the second area,the guide member including an inclined portion inclined upward relativeto the upper surface of the single transparent plate, the inclinedportion being configured to guide the second original scanned by thescanning device in a direction away from the upper surface of the singletransparent plate, wherein at least a portion of the white portion ofthe dividing member is positioned upstream of the guide member in theconveying direction in which the second original being scanned isconveyed at the second area.
 2. The image scanner according to claim 1,wherein the scanning device is configured to scan the white portion ofthe dividing member to obtain white reference data.
 3. The image scanneraccording to claim 1, wherein the white portion of the dividing memberincludes a rectangular portion elongated in the first direction, alength of the rectangular portion in the first direction being shorterthan a length of the dividing member in the first direction.
 4. Theimage scanner according to claim 1, wherein the dividing member furtherincludes a black portion in contact with the upper surface of the singletransparent plate.
 5. The image scanner according to claim 4, whereinthe scanning device is configured to scan the black portion of thedividing member to obtain black reference data.
 6. The image scanneraccording to claim 1, wherein the guide member supports the singletransparent plate.
 7. The image scanner according to claim 1, whereinthe guide member is disposed at an end of the single transparent plate.8. The image scanner according to claim 1, wherein the dividing memberand the guide member are spaced from each other and define the secondarea therebetween.
 9. The image scanner according to claim 1, furthercomprising a feed tray and an exit tray, wherein the conveying device isconfigured to convey the second original along a U-shaped path from thefeed tray to the exit tray via the second area so as to invert thesecond original, and the inclined portion of the guide member defines apart of the U-shaped path.
 10. The image scanner according to claim 1,further comprising a cover configured to pivot relative to the guidemember and cover the first area and the second area of the singletransparent plate, the dividing member, and the guide member.
 11. Theimage scanner according to claim 1, wherein the scanning devicecomprises a contact image sensor.